1. Field of the Invention
The present invention relates to a method for the production of an abrasion-resistant film, in particular for the production of laminate floor materials or abrasion-resistant furniture surfaces, comprising the following steps of the method:                a first application stage in which a decorative paper is provided with an impregnation containing a first synthetic resin,        a second application stage in which a layer which contains a second synthetic resin and particulate abrasion-reducing material is applied to the moist impregnate,        a first treatment stage in which a heat treatment for the partial curing of the synthetic resin and for the partial removal of the moisture from the moist coated impregnate is effected,        a third application stage in which the application of a cover layer containing a third synthetic resin is effected, and        a final second treatment stage in which a heat treatment for removing the moisture is effected.        
Furthermore, the invention relates to an abrasion-resistant finish film, in particular for subsequent adhesive bonding with a carrier for the production of a laminate, consisting of a paper, in particular of a decorative paper, and of a cover layer deposited thereon and consisting of a cured synthetic resin.
2. Background of the Invention
European patent EP 1 068 394 B1 discloses a method for the production of an abrasion-resistant film, in particular for the production of laminate floor materials or abrasion-resistant furniture surfaces, in which, in a first application stage, a decorative paper is provided with an impregnation containing a first synthetic resin, in a second application stage a layer which contains a second synthetic resin and particulate abrasion-reducing material is applied to the moist impregnate, and then a heat treatment is effected which represents a treatment stage for the partial curing of the synthetic resin and for the partial removal of the moisture from the moist coated impregnate.
Said document relates in particular to a method for impregnating decorative papers used for the production of highly abrasion-resistant laminate floor materials, in which the decorative paper is first moistened with an amino resin and impregnated thereby, the amount of the resin being regulated by means of metering rolls, and a layer of amino resin in a special dispersion initially being sprayed onto the moistened wet decorative paper. The final mass per unit area—based on the dry mass of the base paper—is from 100% to 250% and the dispersion contains particulate abrasive material. As equipment for realizing the method, a standard impregnating channel from VITS, which has a slide-in module which in turn consists of an expander roller, a deflection roller, a nozzle orifice with collecting tray, a pair of metering rollers and wire-wound doctor rollers, is arranged after an impregnating unit. The use of such an apparatus is described, for example, in the technical article “New Method for ARP-Manufacturing” by E. Klas and W. Müller in Proceedings of the 2000 TAPPI Plastic Laminats Symposiums, pages 157-165, the abbreviation “ARP”, which has recently been used by those skilled in the art also as an attribute for the nozzle used, representing “Abrasion Resistant Prepreg”. Prepreg in turn is to be understood as meaning pretreated material which was impregnated and was subjected to predrying and partial curing in the sense of the heat treatment mentioned at the outset.
The product of the known method, a decorative paper comprising a uniform coating which has an amino resin with particulate silicon carbide, corundum or aluminum oxide and has no cellulose derivatives, can—as described in the patent—be pressed onto an HDF carrier board on a short-cycle press at 180° C. and with maintenance of a press time of 20 s. Such a board had an abrasion value of IP 12 000 in an abrasion test corresponding to the standard DIN EN 13329.
The abrasion test according to the standard DIN EN 13329 envisages that two friction wheels equipped with emery paper strips are used in a special test apparatus, in the holder of which the test specimens are clamped, where they are brought into contact with the friction wheels. After 100 revolutions in each case, the test specimens are checked for abrasion and the emery paper is replaced by fresh emery paper after 200 revolutions in each case. The test is continued until the so-called initial abrasion point (IP) is reached. This is understood as meaning the point at which, under the conditions defined in detail in the standard, the decorative print present in the test specimen is worn through for the first time in a clearly detectable manner. The number of revolutions required for reaching this point is recorded and is a measure of the abrasion resistance. The abrasion resistance of the laminate floor is then stated in abrasion classes according to the table below.
TABLE 1Abrasion classification according to DIN EN 13329AbrasionRequirement (IP value)classNumber of revolutionsApplicationAC1at least 900 BedroomAC2at least 1500Living roomAC3at least 2000LobbySmall officeAC4at least 4000HotelAC5at least 6000Department store
A similar classification is also to be found in the standard DIN EN 438 “High-pressure decorative laminates (HPL)—boards based on curable resins (laminates)—Part 2: Determination of the properties”.
With regard to the processability of the known product in the press, the following should be noted: the heat treatment which is effected after the application of the additional amino resin layer with the particulate abrasion-reducing material is firstly a drying process in which the water present in the resin material used is removed and secondly is simultaneously a process in which the polymer formation, in particular by solution polycondensation, takes place. In this heat treatment, the technological parameters must be chosen in such a way that no complete crosslinking of the monomers takes place, so that the coated impregnate can be deformed and pressed while still under pressure and at elevated temperature.
In the case of phenol resins which, like the amino resins, in particular melamine-formaldehyde (MF) and melamine-urea-formaldehyde (MUF) resins, are obtained by polycondensation with the use of formaldehyde as one of the main reactants, resole, which is soluble in organic solvents and is processed as casting resin is first formed in the stepwise reaction. At elevated temperature, the resole gives resitol which can still be deformed and pressed under pressure and at elevated temperature, and then, through further condensation, the very hard, crosslinked, insulating material resite which is resistant to chemicals. In the preparation of the aminoplasts, no distinction is made between a resole, resitol and resite state, as in the case of the phenoplasts, but the aminoplasts, too, are first synthesized as oligomeric prepolymers which are crosslinked for final use. The degree of crosslinking which the resin must have in the end product in the process according to EP 1 068 394 B1 therefore corresponds to the resitol state of a phenoplast. In the article cited above, this state has been characterized by “B-stage”.
According to EP 1 068 394 B1, for better processability on the press, flow auxiliaries, such as polyglycol ether, epsilon-caprolactam or butanediol, which are also intended to bring about a better distribution of the particulate material, are also used.
A known method of the type mentioned at the outset is described in DE 199 01 525 A1. This is a method for impregnating and coating paper which is intended for use as a cover layer of an abrasion-resistant laminate, comprising the following steps of the method:                a) a continuous paper web is first impregnated with resin;        b) the paper web is provided on one side with a coating material which contains a liquid resin and fine-particled abrasive material, in particular corundum;        c) the coated paper web is dried;        d) the coating is coated with a cover layer of liquid resin which is free of abrasive particles;        e) the paper web is dried again.        
The known method is intended to ensure that no excessively fast wear is caused on tools and machines by the coated product during subsequent hot pressing.
Both types of films—both those described in EP 1 068 394 B1 and those described in DE 199 01 525 A1—are intended for immediate further processing on a press.
However, apart from these films, which are the result of the known methods, so-called finish films are known which are supplied in roll form and which are subsequently bonded to suitable carriers not by means of a press but with the aid of an adhesive or glue.
In the case of these finish films, as described by way of example in DE 198 46 659 A1, which is considered as being of the generic type with regard to the product having the features at the outset, a particle-free layer consisting of a curable synthetic resin, such as an acrylate, or a layer containing at most nanoparticles, i.e. particles of the molecular order of magnitude—is found for increasing the scratch resistance of the surface, for the composition of which layer specific formulations and modifications which are polymerized by radiation curing with UV light are stated in DE 198 46 659 A1. The scratch resistance is determined on such a layer, in particular according to the standard DIN 53799.